Characterisation and functional mapping of surface potentials in the rat dorsal column nuclei

Abstract

The brainstem dorsal column nuclei (DCN) play a role in early processing ofsomatosensory information arising from a variety of functionally distinct peripheral structures,before being transmitted to the cortex via the thalamus. To improve our understanding of howsensory information is represented by the DCN, we characterised and mapped low- (<200 Hz)and high-frequency (550–3300 Hz) components of nerve-evoked DCN surface potentials. DCNsurface potentials were evoked by electrical stimulation of the left and right nerves innervatingcutaneous structures (sural nerve), or a mix of cutaneous and deep structures (peroneal nerve),in 8-week-old urethane-anaesthetised male Wistar rats. Peroneal nerve-evoked DCN responsesdemonstrated low-frequency events with significantly longer durations, more high-frequencyevents and larger magnitudes compared to responses evoked from sural nerve stimulation.Hotspots of low- and high-frequency DCN activity were found ipsilateral to stimulated nervesbut were not symmetrically organised. In conclusion, we find that sensory inputs from peripheralnerves evoke unique and characteristic DCN activity patterns that are highly reproducible bothwithin and across animals.